31 Years NEET Previous Year Questions: Structural Organisation in Animals - 1 - NEET MCQ

• The smooth muscle fibres taper at both ends (fusiform) and do not show striations.
• The wall of internal organs such as the blood vessels, stomach and intestine contains this type of muscle tissue.
• Smooth muscles are ‘involuntary’ as their functioning cannot be directly controlled.

The cuboidal epithelium is composed of a single layer of cube-like cells. This is commonly found in ducts of glands and tubular parts of nephrons in kidneys and its main functions are secretion and absorption.

Male cockroach bears a pair of short thread-like anal/caudal styles which are absent in females. They project backwardly from the sides of 9^th abdominal segment in male cockroach.

Frog’s heart is myogenic, i.e., heartbeat originates from muscles of heart. Hence, it is autorythmic. Wave of contraction originates from sinus venosus and spreads to wall of sinus venosus and both auricles. This compels the heart to beat. Due to this reason, frog’s heart will continue to beat as long as it gets supply of ATP.

Seminal vesicles are numerous small sacs present on ventral surface of anterior part of the ejaculatory duct which store sperms.

Areolar tissue is the least specialized connective tissue. It has a large amount of ground substance (extracellular material) and possesses rich blood and nerve  supplies. It spreads extensively throughout the body, under the skin and epithelia, in between and around muscles, nerves and blood vessels and in the submucosa of 

Hyaline cartilage is present at the end of long articular bones. It provides a smooth articular surface to permit movement at joints. Elastic cartilage is found where support with  flexibility is needed such as in external ears.
Fibro cartilage is a very tough  substance and is used in places of the body where shock absorbers are needed.
Examples – Discs between vertebrate and in the knee joints.

Hyaline cartilage is firm but slightly elastic with clear matrix. It is present in larynx, trachea, bronchi, nose. Elastic cartilage occur in external ear. Calcified cartilage occurs in suprascapular. Fibrous cartilage occurs in intervertebral discs.

Only nerve cells do not form layers. These also remain structurally separate  from each other. Nerve cells or neurons  are the cells specialized to conduct an electrochemical current. Nerve tissue  is made up of these cells and supporting cells. Epithelial tissue is made of one or a few layers of compactly arranged cells overlying a basement membrane. Glands are epithelial cells specialized to elaborate and release chemicals for use in the body. Muscle tissue is made of elongated and contractile cells called myocytes.

When a bone is kept in dilute acids like HCl for a few days, the Ca salts get dissolved leaving only the soft and flexible organic matrix. This process is called Decalcification. If a bone is kept in KOH it remains unaffected and only the surrounding muscles and connective tissues get dissolved so that the bone now appears clean. 

Simple epithelium is a tissue made of a single layer of compactly arranged cells all of which rest over a noncellular basement membrane.

The chief component of ground  substance of cartilage is chondromuco protein which is formed  of chondroitin sulphate, keratan sulphate and hyaluronic acid.

Mast cells contain granules of heparin and histamine. Heparin prevents blood clotting. Histamine produces inflammation.

Voluntary muscles - under control of our will. Involuntary muscles - Not under control of our will. Muscles of urethra also remain under voluntary control  after infancy.

A skeletal muscle consists of a bundle of long fibres running the length of the muscle. Each fibre is a single cell with many nuclei. Skeletal muscle is also called striated muscle because the regular arrangement of the myofilaments  creates as repeating pattern of  light and dark bands. Each repeating unit is a sarcomere,  the basic functional unit of the  muscle. The borders  of the sarcomere the Z lines, are lined up in adjacent myofibrils and contribute to striations visible with a light microscope.

Basement membrane is a delicate noncellular  layer made of extracellular material that lies below the epithelium in contact with its basal surface. Basement membrane is a delicate noncellular  layer made of extracellular material that lies below the epithelium in contact with its basal surface. Besides this the basal  lamina consists  of mucopoly  saccharides and very fine fibres.

Chondrin is a gelatin-like substance and can be obtained by boiling cartilage in water. The cartilage is a connective tissue that contains cells embedded in a matrix of chondrin.

The simple cuboidal epithelium  consists  of a single layer of polygonal cells which appear cuboidal in vertical section. Cuboidal epithelium occurs in terminal respiratory bronchioles. Columnar epithelium is made of tall cylindrical cells and it occurs in the lining of stomach. In ciliated epithelium the cells bear cilia on their free surface and it occurs in the respiratory tract.

Squamous epithelial cells have the appearance of thin, flat plates. The shape of the nucleus usually corresponds to the cell form and help to identify the type of epithelium. Squamous cells, for example, tend to have horizontal flattened, elliptical nuclei because of the thin flattened form of the cell. They form the lining of cavities such as the mouth, blood vessels, heart and lungs and make up the outer layers of the skin. 

The wall of blood vessels (arteries & veins) are made up of mainly 3 layers – the outer most tunica externa has a loss connective tissue, collagen fibres, lymph vessels and the middle tunica media has circular smooth muscle fibres, some elastic fibres and the inner most tunica interna is a single layered endothelium of polyhedral squamous cells. If the arteries reach organs they form arterioles which are thinner and mainly consist smooth muscles and when they subdivide in the tissues they make capillaries. The wall of capillaries are very thin (usually less than one micron) and have numerous minute pores and made up of only endothelium. Exchange of material takes place between blood and tissue fluid across the endothelial membrane of capillaries through active diffusion.

It is the innermost one celled thick made up of columnar epithelial cells. It lies on a basement. These cells are active & continuously produce new cells by mitotic division that is why called germinative layer or stratum germinativum. The division rate of these cells in highest during sleep or rest and lowest during muscular activity  & stress.

Synthesis of prothrombin which helps in coagulation of blood. Vitamin K is required for the synthesis of prothrombin and blood clotting factors I, VII, IX and X.

The open circulatory system is a type of circulatory system in which nutrients and wastes move freely in the body cavity and not blood vessels. This type of circulatory system is found in insects, molluscs etc. In the case of cockroaches, the open circulatory system is not of a physiological hindrance as circulatory and respiratory systems are not connected. Respiration mainly takes place by special respiratory organs known as spiracles. 

In nervous system afferent nerve fibres carry nerve impulse from receptors or sense organs towards the central nervous  system.

Lymphocyte is a type of white blood cells in the vertebrate immune system. Lymphocytes are responsible for making antibodies.

Characteristics of smooth muscle fibres:

• cells range from 5 to 10 µm  in  diameter and 30 to 200 µm in  length.
• spindle-shaped.    
• single, centrally located nucleus.
• smooth muscle tissue occurs within almost every organ, forming sheets, bundles or sheaths around other tissues.
• Smooth muscle differs from both skeletal and cardiac muscle tissues in structure and function.
• Sarcomeres or myofibrils are not present - therefore not striated, ie. smooth.

• Haversian canal occurs in the humerus. Haversian canals are a series of tubes around narrow channels formed by lamellae.
• This is the region of bone, called cortical bone. Osteons are arranged in parallel to the long axis of the bone. The Haversian canals surround blood vessels and nerve cells throughout the bone and communicate with osteocytes in lacunae through canaliculi.
• This unique arrangement is conducive to mineral salt deposits and storage, which gives the bone tissue its strength.

Lymph differs from blood in a way that it contains less protein and no red blood cells. Lymph contains white blood cells.

Mineral found in red pigment of vertebrate blood is Iron.

In connective tissues, histamine is an organic nitrogen compound involved in local immune responses and regulating physiological function in the gut and acts as a neurotransmitter. Histamine is produced by basophils and by mast cells found in nearby connective tissues.